1. Field of the Invention
The present invention relates to a magnetoresistance-effect element which is applied to a magnetoresistance-effect type head (MR head) or a magnetic sensor (MR sensor).
2. Description of the Background Art
A magnetoresistance-effect element is adapted to detect changes in the electrical resistance of a magnetic film caused by application of a magnetic field, thereby measuring the magnetic field strength and any change thereof. In general, therefore, such a magnetoresistance-effect element must have a high magnetoresistance ratio at room temperature. A magnetic material for the magnetoresistance-effect element is generally prepared from an Fe--Ni alloy (permalloy). However, the Fe--Ni alloy is not preferable as the magnetic material for the magnetoresistance-effect element, due to an extremely small magnetoresistance ratio of about 2 to 3%.
A magnetic multilayer film formed by interposing a non-magnetic thin film between magnetic thin films has been recently proposed in the art. This magnetic multilayer film is preferable as a magnetic material for a magnetoresistance-effect element, due to a high magnetoresistance ratio of about 10%. However, this magnetic multilayer film has a rather complicated structure in which the non-magnetic thin film is interposed between the magnetic thin films, whereby the magnetic thin films provided on both sides of the non-magnetic thin film are at different holding power levels. Thus, the steps required for manufacturing this magnetic multilayer film are disadvantageously complicated.
Physical Review Letters, Vol. 68, No. 25, 22 Jun. 1992, pp. 3745 to 3748 discloses a novel magnetoresistance-effect film. This magnetoresistance-effect film is a CoCu alloy film consisting of Co and Cu, which is atomically mixed with Co that is not in a solid phase but in a liquid phase in a eutectic relation. This alloy film exhibits a high magnetoresistance ratio of at least 10% at an ultra-low temperature of 10K. At room temperature, however, this alloy film exhibits only a small magnetoresistance ratio of about 6 to 7%.